These interfaces may return null in particular cases where the methods and properties are not relevant. They may throw an exception - for example when adding children to a node type for which no children can exist.

Properties

Returns a DOMString representing the base URL. The concept of base URL changes from one language to another; in HTML, it corresponds to the protocol, the domain name and the directory structure, that is all until the last '/'.

Returns a DOMString representing the local part of the qualified name of an element. In Firefox 3.5 and earlier, the property upper-cases the local name for HTML elements (but not XHTML elements). In later versions, this does not happen, so the property is in lower case for both HTML and XHTML.
Though recent specifications require localName to be defined on the Element interface, Gecko-based browsers still implement it on the Node interface.

The namespace URI of this node, or null if it is no namespace. In Firefox 3.5 and earlier, HTML elements are in no namespace. In later versions, HTML elements are in the http://www.w3.org/1999/xhtml namespace in both HTML and XML trees.
Though recent specifications require namespaceURI to be defined on the Element interface, Gecko-based browsers still implement it on the Node interface.

Returns a DOMString containing the name of the Node. The structure of the name will differ with the name type. E.g. An HTMLElement will contain the name of the corresponding tag, like 'audio' for an HTMLAudioElement, a Text node will have the '#text' string, or a Document node will have the '#document' string.

Is a DOMString representing the value of an object. For most Node type, this returns null and any set operation is ignored. For nodes of type TEXT_NODE (Text objects), COMMENT_NODE (Comment objects), and PROCESSING_INSTRUCTION_NODE (ProcessingInstruction objects), the value corresponds to the text data contained in the object.

Is a DOMString representing the namespace prefix of the node, or null if no prefix is specified.
Though recent specifications require prefix to be defined on the Element interface, Gecko-based browsers still implement it on the Node interface.

The methods insertBefore(), replaceChild(), removeChild(), and appendChild() returns one more kind of error (NOT_SUPPORTED_ERR) if called on a Document.
The normalize() method has been modified so that Text node can also be normalized if the proper DOMConfiguration flag is set.
Added the following methods: compareDocumentPosition(), isSameNode(), lookupPrefix(), isDefaultNamespace(), lookupNamespaceURI(), isEqualNode(), getFeature(), setUserData(), and getUserData().
Added the following properties: baseURI and textContent.

The ownerDocument property was slightly modified so that DocumentFragment also returns null.
Added the following properties: namespaceURI, prefix, and localName.
Added the following methods: normalize(), isSupported() and hasAttributes().